Backward light cutting-off apparatus having transmitting light detecting stages and method for detecting transmitting light using the apparatus

Abstract

A optical isolator apparatus suppressing transmission of light in a backward direction having transmitting light detecting stages includes optical fibers respectively arranged at input and output stages without using optical distributers requiring a specifically-processed coating. The apparatus can be used for detecting transmitting light. In other words, without using optical taps requiring a specifically-processed coating. The apparatus includes a first detecting optical fiber adapted to receive multi-reflected light generated in the interior of the optical isolator apparatus and to detect input-stage detection light based on the multi-reflected light and, a first lens adapted to collimate the input signal light. An output optical fiber is adapted to transmit an output signal light. A second detecting optical fiber is adapted to detect backward light reflected from the output optical fiber and introduced again in the interior of the optical isolator apparatus.

What is claimed is: 
     
       1. An optical amplifier, comprising: an input optical fiber transmitting an input signal light to an output-stage in a forward direction, the input signal light being transmitted in the forward direction when the input signal light is transmitted in a direction from the input optical fiber to the output-stage;   a first detecting optical fiber transmitting a first detection-stage signal indicating a state of the input signal light to a control unit;   an input-stage isolator unit suppressing transmission in a backward direction of the input signal light, the backward direction being opposite to the forward direction;   an excited light source amplifying the input signal light when the input signal light is weaker than a predetermined level;   a wavelength division multiplexer receiving an optical signal having a first wavelength emitted from the excited light source when the input signal light is weaker than the predetermined level, receiving the input signal light from the input-stage backward cutting-off unit having a second wavelength, coupling the received optical signal and input signal light to form a coupled signal, and outputting the coupled signal in the forward direction; an amplifying fiber amplifying the coupled signal received from the wavelength division multiplexer, and outputting an amplified optical signal in the forward direction;   a second detecting optical fiber transmitting a second detection-stage signal, indicating a gain state of the amplified optical signal, to the control unit;   an output-stage backward light cutting-off unit suppressing transmission in the backward direction of the amplified optical signal, and receiving the amplified optical signal from the amplifying fiber;   an output optical fiber receiving the amplified optical signal from the output-stage backward light cutting-off unit and transmitting the amplified optical signal to the output-stage;   a third detecting optical fiber transmitting a third detection-stage signal, indicating a state of light reflected from the output optical fiber toward the output-stage backward light cutting-off unit, to the control unit; and   the control unit detecting the first, second and third detection-stage signals, and controlling the excited light source.   
     
     
       2. The optical amplifier of claim 1, wherein the first detection-stage signal is transmitted from the input-stage backward light cutting-off unit to the control unit, and the second and third detection-stage signals are transmitted from the output-stage backward light cutting-off unit to the control unit. 
     
     
       3. The optical amplifier of claim 1, wherein the control unit uses an electrical signal to drive the excited light source. 
     
     
       4. The optical amplifier of claim 2, wherein the control unit uses an electrical signal to drive the excited light source. 
     
     
       5. An optical amplifier comprising: an input optical fiber transmitting input signal light to an output-stage in a forward direction, the input signal light being transmitted in the forward direction when the input signal light is transmitted in a direction from the input optical fiber to the output-stage;   a first detecting optical fiber transmitting a first detection-stage signal, indicating a state of the input signal light, to a control unit;   a backward light cutting-off apparatus suppressing a transmission of the input signal light in a backward direction opposite to the forward direction;   a first output optical fiber transmitting in the forward direction the input signal light passing through the backward light cutting-off apparatus;   an excited light source amplifying the input signal light when the input signal light is weaker than a predetermined level;   a wavelength division multiplexer coupling an optical signal emitted from the excited light source with the input signal light received from the backward light cutting-off apparatus, and outputting a coupled signal in the forward direction;   an amplifying fiber amplifying the coupled signal received from the wavelength division multiplexer and outputting an amplified signal in the forward direction;   a second detecting optical fiber transmitting a second detection-stage signal, indicating a state of light reflected from the first output optical fiber, to the control unit;   an optical system cutting off a transmission in the backward direction of the amplified signal received from the amplifying fiber;   a second output optical fiber transmitting the amplified signal received from the optical system to an output-stage; and   the control unit adapted to detect the first and second detection-stage signals, and controlling the excited light source.   
     
     
       6. The optical amplifier of claim 5, wherein the first and second detection-stage signals are transmitted from the backward light cutting-off unit to the control unit. 
     
     
       7. The optical amplifier of claim 6, wherein the control unit utilizes an electrical control to drive the excited light source. 
     
     
       8. The optical amplifier of claim 5, wherein the control unit utilizes an electrical control to drive the excited light source. 
     
     
       9. The optical amplifier of claim 5, wherein the backward light cutting-off apparatus comprises: a primary input optical fiber transmitting input signal light to a primary output-stage;   a primary detecting optical fiber apparatus receiving multi-reflected light generated in an interior of the backward light cutting-off apparatus and detecting input-stage detection light upon receiving the multi-reflected light;   a first support unit supporting the primary input optical fiber and the primary detecting optical fiber apparatus;   a first lens collimating the input signal light emerging from the primary input optical fiber in the forward direction;   a primary output optical fiber transmitting an output signal light upon receiving, the input signal light;   a secondary detecting optical fiber apparatus receiving and detecting backward light reflected from the primary output optical fiber and introduced into the interior of the backward light cutting-off apparatus, and detecting detection light at the apparatus output-stage; and   a second support unit supporting the primary output optical fiber and the secondary detecting optical fiber apparatus.   
     
     
       10. A backward light cutting-off apparatus, comprising: an input optical fiber transmitting input signal light to an output-stage;   a first detecting optical fiber receiving multi-reflected light generated in an interior of the apparatus and detecting input-stage detection light upon receiving the multi-reflected light;   a first ferrule supporting the input optical fiber and the first detecting optical fiber;   a first lens collimating the input signal light emerging from the input optical fiber;   an output optical fiber transmitting an output signal light upon receiving the input signal light;   a second detecting optical fiber detecting backward light reflected from the output optical fiber and introduced into the interior of the apparatus, and detecting detection light at the output stage; and   a second ferrule supporting the output optical fiber and the second detecting optical fiber.   
     
     
       11. The apparatus of claim 10, wherein the first and second detecting optical fibers are respectively located at the input stage and the output stage. 
     
     
       12. The apparatus of claim 10, wherein the first detecting optical fiber detects the state of the input signal light at the input stage, and the second detecting optical fiber detects the state of light reflected from the output stage and conveyed to the apparatus. 
     
     
       13. The apparatus of claim 10, wherein the first detecting optical fiber detects the input stage detection light, by receiving the multi-reflected light reflected between the input optical fiber and the lens. 
     
     
       14. The apparatus of claim 12, wherein the first detecting optical fiber detects the input stage detection light, by receiving the multi-reflected light reflected between the input optical fiber and the lens. 
     
     
       15. The apparatus of claim 10, wherein the second detecting optical fiber detects the output stage detection light, by receiving a portion of the backward light reflected from the output stage and introduced in the second detecting optical fiber. 
     
     
       16. The apparatus of claim 12, wherein the second detecting optical fiber detects the output stage detection light, by receiving a portion of the backward light reflected from the output stage and introduced in the second detecting optical fiber. 
     
     
       17. The apparatus of claim 10, further comprising; a first polarizer splitting the input signal light collimated by the first lens into vertically-polarized light beams and horizontally-polarized light beams;   a polarized light phase rotator shifting phases of the vertically-polarized light beams of the input signal light and the horizontally-polarized light beams split by the first polarizer;   a second polarizer concentrating the light beams phase-shifted by the polarized light phase rotator; and   a second lens collimating the input signal light emerging from the second polarizer into an output optical fiber.   
     
     
       18. The apparatus of claim 17, wherein the first detecting optical fiber detects the state of the input signal light at the input stage, and the second detecting optical fiber detects the state of light reflected from the output stage and conveyed to the apparatus. 
     
     
       19. The apparatus of claim 17, wherein the second detecting optical fiber detects the output stage detection light, by receiving light reflected between the output optical fiber and the second lens. 
     
     
       20. The apparatus of claim 18, wherein the second detecting optical fiber detects the output stage detection light, by receiving light reflected between the output optical fiber and the second lens. 
     
     
       21. A method for detecting transmitting light using the backward light cutting-off apparatus of claim 10, comprising the steps of: detecting the state of the input signal light by: converting a portion of the input signal light conveyed to the first lens by the input optical fiber into the multi-reflected light between the input optical fiber and the first lens,   introducing the multi-reflected light into the first detecting optical fiber, and detecting the multi-reflected light; and     detecting the state of the output signal light by: collimating the input signal light conveyed from the input optical fiber to the first lens while sequentially passing the input signal light through the first lens, the first polarizer, the polarized light phase rotator, the second polarizer and the second lens, converting the collimated input signal light into output signal light, and transmitting the output signal light,   reflecting the output signal light by a medium to backwardly introduce the output signal light into the backward light cutting-off apparatus through the output optical fiber,   partially converting the backward light into reflected light between the second lens and the output optical fiber,   introducing the reflected light in the second detecting optical fiber, and detecting the reflected light.     
     
     
       22. A method for detecting transmitting light using the backward light cutting-off apparatus of claim 10, comprising the steps of: detecting the state of the input signal light by: converting a portion of the input signal light conveyed to the first lens by the input optical fiber into the multi-reflected light between the input optical fiber and the first lens,   introducing the multi-reflected light into the first detecting optical fiber, and detecting the multi-reflected light; and     detecting the state of the output signal light by: collimating the input signal light conveyed from the input optical fiber to the first lens while sequentially passing the input signal light through the first lens, the first polarizer, the polarized light phase rotator, the second polarizer and the second lens, converting the input signal light into the output signal light, and transmitting the output signal light,   reflecting the output signal light by a medium to backwardly introduce the output signal light into the backward light cutting-off apparatus through the output optical fiber,   partially converting the backward light into reflected light between the second lens and the output optical fiber, introducing the reflected light in the second detecting optical fiber, and detecting the reflected light.     
     
     
       23. A method for detecting transmitting light using a backward light cutting-off apparatus, comprising the steps of: detecting a state of input signal light by: converting a portion of the input signal light conveyed to the first lens by an input optical fiber into multi-reflected light between the input optical fiber and a first lens,   introducing the multi-reflected light into a first detecting optical fiber, and detecting the multi-reflected light; and     detecting a state of output signal light by: collimating the input signal light conveyed from the input optical fiber to the first lens while sequentially passing the input signal light through the first lens, a first polarizer, a polarized light phase rotator, a second polarizer and a second lens, converting the input signal light into the output signal light, and transmitting the output signal light,   reflecting the output signal light by a medium to backwardly introduce the output signal light into the backward light cutting-off apparatus through an output optical fiber, partially converting the backward light into reflected light between the second lens and the output optical fiber,   introducing the reflected light in a second detecting optical fiber, and detecting the reflected light.